Optical proximity sensors, such as the AVAGO TECHNOLOGIES™ HSDL-9100 surface-mount proximity sensor, the AVAGO TECHNOLOGIES™ APDS-9101 integrated reflective sensor, the AVAGO TECHNOLOGIES™ APDS-9120 integrated optical proximity sensor, and the AVAGO TECHNOLOGIES™ APDS-9800 integrated ambient light and proximity sensor, are known in the art. Such sensors typically comprise an integrated high efficiency infrared emitter or light source and a corresponding photodiode or light detector, and are employed in a large number of hand-held electronic devices such as mobile phones, Personal Data Assistants (“PDAs”), laptop and portable computers, portable and handheld devices, amusement and vending machines, industrial automation machinery and equipment, contactless switches, sanitary automation machinery and equipment, and the like.
Referring to FIG. 1, there is shown a prior art optical proximity sensor 10 comprising infrared light emitter 16, light emitter driving circuit 51, light detector or photodiode 12, light detector sensing circuit 53, metal housing or shield 18 with apertures 52 and 54, and object to be sensed 60. Light rays 15 emitted by emitter 16 and reflected as light rays 19 from object 60 (which is in relatively close proximity to optical proximity sensor 10) are detected by photodiode 12 and thereby provide an indication that object 60 is close or near to sensor 10.
As further shown in FIG. 1, optical proximity sensor 10 further comprises metal housing or shield 18 formed of metal and comprising apertures 52 and 54 located over light emitter 16 and light detector 12, respectively, such that at least a first portion of light 15 emitted by light detector 12 passes through aperture 52, and at least a second portion of the first portion 19 of light reflected from object 60 in proximity to sensor 10 passes through aperture 54 for detection by light detector 12. As shown, metal housing or shield 18 may further comprise first and second modules 61 and 63 within which light emitter 16 and light detector 12 are disposed, respectively. The first and second modules 61 and 63 comprise adjoining optically opaque metal inner sidewalls 25 to provide optical isolation between first and second modules 61 and 63. Many optical proximity sensors generally include a metal shield, such as shield or housing 18 of the type shown in FIG. 1, to provide optical isolation between light emitter 16 and light detector or photodiode 12 so that undesired optical cross-talk between emitter 16 and detector 12 is minimized.
FIG. 2 shows a prior art optical proximity sensor 10 with a more complicated metal shield or housing 18 than that of FIG. 1. The optical proximity sensor shown in FIG. 2 is an AVAGO TECHNOLOGIES™ APDS-9800 Integrated Ambient Light and Proximity Sensor, which contains a printed circuit board (“PCB”) substrate 11 upon which are mounted LED 16, light detector or photodiode 12, and ambient light sensor 14. The two-piece metal shield 18 covers LED 16, light detector or photodiode 12, and ambient light sensor 14 and contains a downwardly projecting light barrier 25 disposed therebetween. In the APDS-9800 optical proximity sensor, metal shield 18, being of a considerably more complicated shape and geometry than that of FIG. 2, is formed and thinned using progressive metal stamping techniques, and must be hand-fitted and attached to the underlying PCB by gluing to ensure proper alignment and fit.
As will now be seen, at least some optical proximity sensors of the prior art rely upon the use of an externally mounted metal shield 18, which is required to reduce the amount of crosstalk or interference that might otherwise occur between LED 16 and light detector 12, as well as to help increase the detection distance of the device. Metal shields 18 are quite small, however, making them difficult to manufacture in high volumes, and thus expensive to fabricate. Such metal shields 18 also generally require expensive automated equipment to attach same to sensors 10 in a mass production setting. Moreover, the quality of metal shields 18 often varies, and issues can arise with suppliers being unable to meet the tight dimensional tolerances required for such small devices. Metal shields 18 can also detach from sensor 10, thereby adding another failure point for sensor 10.
In addition, the commercial marketplace demands ever smaller portable electronic devices. This of course means there exists a strong motivation to make optical proximity sensors ever smaller. As optical proximity sensors become smaller, it becomes increasingly difficult to manufacture and attach the aforementioned metal shields to the sensors in a mass production setting. The metal shields themselves also add to the bulk and volume of the resulting sensor or package.
What is need is an optical proximity sensor design that eliminates the need to include a metal shield 18, but which retains high crosstalk and interference rejection characteristics so that an optical proximity sensor can be provided that features improved performance, lower cost, increased manufacturability and improved reliability. What is also needed is a smaller optical proximity sensor.